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Difficulty: MediumSeparating Funnel and Solvent Extraction

In a laboratory setup, a student attempts to isolate an organic solute from an aqueous solution by solvent extraction using a separating funnel. If the student incorrectly selects ethanol instead of ethoxyethane as the extracting solvent, why will the separation fail?

  1. Ethanol is completely miscible with water, preventing the formation of two distinct liquid layers.Answer
  2. B
    Ethanol has a lower boiling point than water, causing the solvent to vaporize before extraction can occur.
  3. C
    Ethanol is less dense than water, which forces the organic solute to remain permanently in the lower layer.
  4. D
    Ethanol reacts chemically with aqueous solutes, converting them into insoluble trioxocarbonate salts.

Answer

Ethanol is completely miscible with water, preventing the formation of two distinct liquid layers.
The successful use of a separating funnel for solvent extraction requires two immiscible liquid phases. Ethanol is completely miscible with water due to extensive hydrogen bonding, forming a single homogeneous mixture rather than two separate layers.

Step-by-Step Solution

1
Identify the key requirement for using a separating funnel in solvent extraction.
The extracting solvent must be immiscible with the solvent containing the solute (usually water) so that two separate physical phases form.
Solvent extraction relies on the partitioning of a solute between two immiscible liquid layers.
2
Analyze the solubility behavior of ethanol when added to water.
Ethanol forms strong hydrogen bonds with water molecules, making them completely miscible in all proportions.
Because ethanol and water mix homogeneously into a single phase, no interface or separate layers can form in a separating funnel.
3
Conclude why ethoxyethane (diethyl ether) works while ethanol fails.
Ethoxyethane is immiscible with water and forms a separate upper layer, whereas ethanol mixes completely and cannot separate.
Immiscibility is mandatory for phase separation.

Key Concept

Liquid-liquid immiscibility requirement in solvent extraction
Estimated Time:1m 0s
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Topics

Separating Funnel and Solvent Extraction

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